Fuel cell power plants require a source of hydrogen in order to generate electrical power. A conventional method for the production of hydrogen is the reaction of hydrocarbon gases or other fluids with steam in the presence of a catalyst to produce a hydrogen containing gas. Generally, the hydrocarbon that is subjected to the steam reforming process is first desulfurized to avoid poisoning of the reforming catalyst. In a hydrodesulfurization process, the hydrocarbon is treated catalytically in the presence of hydrogen to effect a conversion of the organic sulfur compounds to inorganic compounds which are subsequently removed by absorption.
In U.S. Pat. No. 5,769,909, a fuel gas stream hydrodesulfurizer assembly is thermally coupled with process gas heat exchangers and a shift converter. The high temperature gas stream from the reformer in the power plant is also used to heat steam which is fed to the reformer assembly. The assembly cools the process gas stream from the steam reformer to temperatures which are suitable for the shift conversion reaction.
The hydrodesulfurizer bed includes both the necessary catalyst, and also the necessary hydrogen sulfide absorbent all in one bed. Additionally, the temperature of the natural gas stream entering the hydrodesulfurizing bed must be elevated to a temperature which best promotes the catalytic conversion of sulfur and sulfur compounds to hydrogen sulfide.
The system described in the aforesaid patent was found to not sufficiently heat the raw fuel and hydrogen mixture to a sufficiently high temperature for maximum catalytic conversion of organic sulfur containing compounds in the feedstock to hydrogen sulfide.